It is known, for example, according to the paper by Donald A. Shaw and Terrence C. Tuominen, which appeared in Synthetic Communications 15(14), 1291-1297 (1985), to prepare 3-hydroxy-3-trifluoromethyl phthalide, which can be used as a plant growth regulator, in three stages. The starting materials employed are bromotoluene and an amide of trifluoroacetic acid, of the formula CF.sub.3 CONCH.sub.3 (OCH.sub.3), in the presence of magnesium in ether. The starting materials, especially the amide of trifluoroacetic acid, are not readily available. In addition, industry has always been reluctant to use a highly reactive magnesium derivative because of process economy and safety aspects.
It is also known, according to a paper by Prabhu, Eapen and Tamborski, which appeared in J. Org. Chem. 1984, 49, 2792-2795, to prepare the same product as in the preceding paper by a different process. The process according to this paper starts with a dibromo derivative which is condensed with butyllithium at -110.degree. C. The use of alkyllithium derivatives, however, has always been avoided in industry for safety reasons, as these derivatives are highly flammable.
Thus, industry continues to search for a process which is economically satisfactory, and secure with regard to safety, for preparing the various prefluorinated ketones and alcohols required by the agrochemical and pharmaceutical industries.